Please ensure you are using the latest version.
The app currently has 2 login prompts - the first one is for VoIP only and the second one is for the rest of the app. If you do not use the VoIP calling method, you can leave the first login prompt blank.
If you are using 2 step/factor authentication, please make sure you use an App Password
for the first login prompt only.
Also, because Google doesn't provide secure authentication APIs for Google Voice, you must enable "Allow less secure apps"
option on your Google account.